I am trying to find out what size of mufler is appropiate. I know shorter is louder but I thought there was a minimal size for certain engines. I have a 94 351W. I am looking at uying a Magnaflow 4X9 wich is on sale for $60.

Thanks

 

There really is no minimal size, depends on what sound and how loud you want it. The biggest thing to look for (and sometimes its hard to find) is the flow rate of the muffler. You could get a huge muffler, but if it doesnt flow any better than the stocker, its a waste of time.

Magaflows have great flow rates, and you should be ok with that 4x9. However, if your looking for loudness, you should probably look elsewhere.

 

i'm no expert by any means but i just had my muffler replaced with a flowmaster knock-off and although it sounds good it was about half the size of the one that came off my expedition (98).

i immediately asked him why he would put something on so small when the other one was huge and he said it didn't really matter and that one would do the same job but give me better sound.

well, ever since i had this one in there my gas mileage had definitely decreased for whatever reason. i am now getting about 11mpg when i was getting close to 14mpg before.

i am about to start a thread asking about how this could happen as i am ready to take this back to the shop and ask them to change it.

i took of the negative battery cable in hopes that the computer would adjust to the new muffler but it hasn't changed that i can tell.

best wishes with your decision and i hope this helps.